Drug interactions Flashcards
Alcohol
- CNS depressans
- additive CNS depression, sedation, ataxia, increased risks of accidents
- Acetaminophen
- Increased formation of hepatotoxic metabolites of acetamonophen
Antacid
- Digoxin, iron supplements, fluoroquinolones, ketoconazole, tetracyclines, thyroxine
- Decreased gut absorption due to either to reaction with the affected drug or due to reduced acidity
Antihistamines
- Antimuscarinis, sedatives
- Additive effects with the drugs affected
Antimuscarnic drugs
- Drugs absorbed from the small intestine
- Slowed onset of effect because stomach emptying is delayed
Barbiturates (phenobarbital)
- Azoles, CCB, cyclosporine, propanol,protease inhibitors, quinidine, steroids, warfarin, kinase inhibitors, methadone, ansd many other drugs metabolzied in the liver
- Increased clearance of the affected drugs due to enzyme induction, possibly leading to decreases in drug effectiveness
Beta blockers
- Insulin
- masking of symptoms of hypoglycemia
- Prazosin
- increased first dose syncope
Bile acid-binding resins
- Acetaminophen, digitalis, thiazides, thyroxine
- Reduced abdorption of the affected drug
Carbamazepine
Cyclosporine, lidocaine, phenytoin, propanolol, quinidine, theophylline, warfarin, dofetilide
Reduced effect of other drugs because of induction of metabolism
Cimetidine
BZ, lidocaine, phenytoin, propanol, quinidine, theophylline, warfarin, dofetilide
Risk of toxicity due to inhibition of metabolism or reduced renal excretion
Disulfiram, metronidazole, certain cephalosporins
Ethanol
Increased hangover effect due to inhibition of aldehyde dehydrogenase
Erythromycin
Carbamazepine, cisaparide, quinidine, sildenafil, SSRIs
Risk of toxicity due to to inhibition of metabolism
Furanocoumarins (grapefruit)
Alprazolam, atorvastatin, cyclosporine, midazolam, nifedipine
Risk of toxicity due to inhibition of metabolism
ketoconazole and other azoles
Benzodiazepines, cisapride, cyclosporine, fluoxetine, lovastatin, omeprazole, quinidine, tolbutamide, oral anticoagulants (warfarin, apixaban, rivaroxaban)
Risk of toxicity due to inhibition of metabolism, Increased bleeding with oral anticoagulants, myopathy with statins
MAO inhibitors
- Catecholamine releasers (amphetamine, ephedrine)
- Increased norepinephrine in sympathetic nerve endings released by the interacting
- Tyramine-containing foods and beverages
- hypertensive crisis
NSAIDs
- Anticoagulants
- Increased bleeding tendency because of reduced platelt aggregation
- ACE inhibitors
- Decreased hypertensive efficacy of ACE inhibitor
- Loop diuretics
- reduced diuretic efficacy
Phenytoin
Doxycycline, methadone, quinidine, steroids, verapamil, anticoagulants
Reduced effect of other drugs because of induction of metabolism
Rifampin
Azole antifungal drugs, corticosteroids, methadone, sulfonylureas, oral anticoagulants
Reduced effect of other drugs because of induction of metabolism
Ritonavir
Benzodiazepines, cyclosporine, diltiazem, HMG-CoA reductase inhibitors, lidocaine, metoprolol, other HIV protease inhibitors, SSRIs
Risk of toxicity due to inhibition of metabolism
Salicylates
- Corticosteroids
- Additive toxicity to gastric mucosa
- Heparin, oral anticoagulants
- increased bleeding tendency
- MEthotrexate
- decreased clearance, causing greater methotrexate toxicity
- Sulfinpyrazone, probenecid
- Decreased uricosuric effect
SSRIs
MAO inhibitors, meperidine, TCA, St. John’s wort
Serotonin syndrome (hypertension, tachycardia, muscle rigidity, hyperthermia, seizures)
thiazides
- Digitalis
- increased risk of digitalis toxicity because thiazides diminish potassium stores
- Lithium
- Increased plasma levels of lithium due to decreased total body water
A 55 year old patient currently receiving a drug for a psychiatric condition is to be starred on diuretic therapy for mild heart failure. Consideration should be given to the fact that thiazides are known to reduce the excretion of what drug_______
lithium
A hypertensive patient has been using nifedipine for some time without untoward effects. If he experiences a rapidly developing enhancement of the antihypertensive effect of the drug, it is most likely due to
Furacocoumarins in grapefruit juice
A patient suffering from a depressive disorder is being treated with imipramine. If he uses diphenhydramine for allergic rhinitis, a drug interaction is likely to occur because
Both drugs block muscarinic receptors
If phenelzine is administered to a patient taking fluoxentine, which of the following is most likely to occur?
Agitation. muscle rigidity, hyperthermia, seizures
Ajis a 45 year old man participating in a drug rehab program that supplies daily methadone. AJ reports that he needs more methadone to avoid withdrawal, since he started treatmetn for his tuberculosis. What drug might have caused this?
Rifampin
The antihypertensive effects of captopril can be antagonized by which of the following?
NSAIDs
Which drug has resulted in severe hematoxicity when adminsitered to a aptient being treated with azathioprine?
Allopurinol
In patients with HIV infection, the inhibitory action of this agent on drug metabolism has clinical value
Ritonavir
The drug enhances the toxicity of methotrexate by decreasing its renal clearance
Ibuprofen
Concomitant use of St. John’s wort is reported to increase the effectivity of ______
Ibuprofen
